A long term evolution (Long Term Evolution, abbreviated as “LTE”) release 8/9/10 (Release 8/9/10, abbreviated as “Rel-8/9/10”) communication system uses a dynamic scheduling technology to improve the performance of the communication system. That is, a base station (Evolved NodeB, abbreviated as “eNB”) schedules and allocates resources according to channel conditions of each user equipment (User Equipment, abbreviated as “UE”), so that each scheduled user equipment performs transmission on its optimal channel. In a downlink transmission, the eNB sends, according to a dynamic scheduling result, a physical downlink shared channel (Physical Downlink Shared Channel, abbreviated as “PDSCH”) and a corresponding physical downlink control channel (Physical Downlink Control Channel, abbreviated as “PDCCH”) to each scheduled user equipment, where the PDSCH carries data sent by the eNB to the scheduled user equipment and the PDCCH is mainly used to indicate the corresponding PDSCH transmission format, that is, scheduling information, including resource allocation, a transport block size, a modulation and coding scheme, a transmission rank, precoding matrix information, and the like.
The PDCCH and the PDSCH are time division multiplexed into one subframe. Therefore, the number of PDCCHs that can be supported by one subframe is limited, that is, the number of user equipments scheduled by the base station is limited. The limited capacity of the PDCCH is more serious during further evolution of the LTE Rel-10 communication system. In particular, the evolved system generally uses a multiple-input multiple-output (Multiple Input Multiple Output, abbreviated as “MIMO”) technology to increase the spectrum efficiency of the communication system. This means that the quantity of user equipments concurrently scheduled by the base station is increased, and therefore more PDCCHs are needed. In addition, an important scenario considered in the evolved system is a heterogeneous network. A specific implementation manner of this scenario is as follows: In addition to macro base stations, a plurality of remote radio units (Remote Radio Unit, abbreviated as “RRU”) is set in the coverage of a macro cell, where the RRUs have the same cell identity as that of the macro cell, and each RRU can serve some user equipments independently since the PDCCH uses a demodulation reference signal (Demodulation Reference Signal, abbreviated as “DMRS”)-based transmission manner. However, each RRU is transparent for the user equipment. Therefore, in this scenario, the quantity of user equipments scheduled by the base station is greatly increased, and accordingly, the required capacity of the PDCCH is also increased.
Therefore, the communication system enhances the existing PDCCH, that is, it splits some resources from an original PDSCH area to transmit an enhanced PDCCH, that is, an enhanced physical downlink control channel (Enhanced Physical Downlink Control Channel, abbreviated as “E-PDCCH”). In this way, resources allocated to a control channel are very flexible, and the capacity of the PDCCH is enlarged. In addition, the E-PDCCH may also use the DMRS-based transmission manner, so that a space can be reused to improve transmission efficiency of the control channel. For example, control channels of user equipments serving under different RRUs can occupy the same time frequency resource so long as the control channels are spatially isolated.
In the LTE Rel-8/9/10 communication system, a hybrid automatic repeat request (Hybrid Automatic Repeat Request, abbreviated as “HARQ”) technology is generally used to improve the performance of the communication system, and the HARQ technology continues to be applied in an evolved communication system, for example, LTE Rel-11. Because a dynamically scheduled user equipment needs to feed back uplink acknowledgement (Acknowledgement, abbreviated as “ACK”)/non-acknowledgment (Non-Acknowledgement, abbreviated as “NACK”) information to the eNB, the dynamically scheduled user equipment needs to determine a resource used to feed back uplink ACK/NACK information. In consideration of randomness of dynamic scheduling and resource utilization, a resource used to feed back the uplink ACK/NACK information needs to be reserved by using a dynamic reservation method rather than by using a semi-static reservation method, that is, a resource is reserved only when the PDSCH is scheduled. Therefore, for a communication system using the HARQ technology, the technical issue to be solved is how to dynamically determine a resource used to feed back the uplink ACK/NACK information after the user equipment detects an E-PDCCH and a PDSCH.
In related technologies, in the case where the PDCCH and the PDSCH are multiplexed together, that is, in the case where the PDCCH is not enhanced, the ACK/NACK information is fed back by using a code division multiplexing manner on a physical uplink control channel (Physical Uplink Control Channel, abbreviated as “PUCCH”), that is, each user equipment modulates the ACK/NACK information by using a sequence of time-frequency two dimensional spread spectrum, and then sends the modulated ACK/NACK information. For each dynamically scheduled user equipment, a resource used to feed back the uplink ACK/NACK information is implicitly determined by a sequence number of a control channel element (Control Channel Element, abbreviated as “CCE”) of the PDCCH.
However, in the case where the PDCCH, the E-PDCCH, and the PDSCH are multiplexed together, if the method for determining, by using the sequence number of the CCE, a resource used to feed back the uplink ACK/NACK information in the related technologies is still used, E-PDCCHs using the DMRS-based transmission manner under different RRUs may occupy the same time frequency resources and different DMRS ports, different E-PDCCHs are likely to have the same control channel logical number or sequence number. Therefore, this may cause a problem of conflict on the resource used to feed back ACK/NACK information between different user equipments, that is, two or more user equipments occupy the same resource, thereby imposing interference on the ACK/NACK information between different user equipments.